Couple of pointers...
You did link to a place that makes memorable T-shirts with icons of your hometown. Just click on the link in your post and you are there.
For a picture the URL has to point to a jpg or gif file posted somewhere on the net. Right click on the picture you want and left click on Properties that will give you it's URL Then click on the IMG button and then paste the URL and click on the Ing button again like:
Custom Avatars are explained here:
If you can't reduce the size to fit, email the picture to me and I'll try to resize it for you.
Navigating is explained here:
There are a few more tricks you will find as you use the software.